I plan to determine the arrangement of both repetitious and non-repititious sequences in a piece of DNA isolated from Drosophila melanogaster chromosomes. This piece of DNA will be isolated by enzymatically inserting Drosophila molecules into plasmid DNA and using the resultant hybrid molecules to transform bacteria. Large numbers of identical copies of a single transforming hybrid can be extracted from a clone transformant. One population of identical copies (the parent population) will be selected for this study of sequence arrangement. By using a combination of electron microscopic and reassociation kinetic techniques it will be possible to map the repetitive and non-repetitive sequences within this selected segment. The mapped resolution should be at about 100 bases. Bibliographic reference: P.C. Wensink, D.J. Finnegan, J.E. Donelson, and D.S. Hogness, A System for Mapping DNA Sequences in the Chromosomes of Drosophila melanogaster, Cell 3, 315, 1974.